1. Field of the Invention
The present invention relates to over-discharge protection circuit by, and more particularly, to over-discharge protection circuitry for the battery charging circuit in a portable apparatus, for example, a portable cordless (wireless) telephone.
2. Description of the Related Art
Portable cordless telephones, for example, usually comprise a portable portion (handset) and a body portion. The handset is provided with a dial or push buttons, a transmitter-receiver and a chargeable battery, and the body is provided with a transmitter-receiver and a battery charger and is connected to a telephone cable. The charge circuit is made up of a chargeable battery in the handset and a battery charger in the body. The battery charger is connected to the chargeable battery through two contact points and the chargeable battery is charged while the telephone is not in use, so as to recover the power discharged by the chargeable battery during use of the telephone.
A problem arises, however, while the chargeable battery is being charged by the battery charger. Namely, when the power source for the battery charger is turned OFF during the charging of the battery, the battery discharges power through a load (dial portion, transmitter-receiver, etc.), and if this discharging state is not interrupted, an over-discharge of the battery will occur. This problem is explained in detail hereinafter.